pub fn odd_fibnacci_sum(threshold: u32) -> u32 {
    let mut f1 = 0;
    let mut f2 = 1;
    let mut sum = 1;
    for _ in 2..threshold {
        let f3 = f1 + f2;
        if f3 > threshold {
            break;
        }
        if f3 % 2 == 1 {
            sum += f3;
        }
        f1 = f2;
        f2 = f3;
    }
    sum
}
